The present invention relates to a non-return valve for bore hole sleeves which are intended for injection of a sealing and/or reinforcing compound into rock cracks and similar cracks and which comprise a rigid case, one end of which is provided with means for detachable connection to the case of a pump hose for the compound to be injected, as well as an expandable device for securing the rigid case in the bore hole.
When bore hole sleeves are used, said sleeves are first fixed by means of the expandable device in holes that have been bored in the rock. The sealing and/or reinforcing compound is then injected through the bore hole sleeves into the rock crack. The bore hole sleeves have to be provided with a non-return valve of some type to prevent the compound from flowing back through the bore hole sleeves, when the pump pressure ceases.
The non-return valves which hitherto have been used in connection with bore hole sleeves have comprised a movable mechanical valve means, for example a ball, as disclosed in the German Patent Application No. 2 402 509. A non-return valve of this type has two disadvantages. Firstly, it is difficult to achieve a reliable operation of the valve means during the heavy working conditions prevailing during injection of, for example, cement grout or a similar sealing compound under high pressure into rock cracks. Secondly, the valve element obstructs the injection of the compound due to the fact that the flow area of the bore hole sleeve is reduced. It is particularly difficult to use a ball valve as non-return valve in connection with a bore hole sleve of the type disclosed in the Swedish Patent Application No. 8204256-5, where a blocking means is provided at the exit end of the bore hole sleeve to enable the establishment of an initial pressure in the bore hole sleeve to actuate the expandable means. The blocking means is then forced out of the bore hole sleeve by further increasing the pressure in the bore hole sleeve. Furthermore, non-return valves comprising balls or other movable valve means and corresponding valve seats are expensive to manufacture.